The invention relates to a system and method for remote analysis of emissions from vehicles with small engines, such as motorcycles.
Internal combustion engines produce gaseous by-products during operation. Many of these gaseous by-products pollute the environment and, in high concentrations, can be extremely harmful. The cumulative effect of these pollutants, especially from automobiles and other vehicles, has had a significant impact on air quality and ozone depletion throughout the world.
In order to curb vehicle emissions, many states have instituted Inspection and Maintenance (IM) programs. Some IM programs include periodic inspections conducted at state run facilities. These inspections involve operating the vehicle through a series of accelerations, decelerations, stops, and starts on a chassis dynamometer and collecting the vehicle""s emissions in an analyzer. These inspections take time and are inconvenient for vehicle owners.
To this end, remote sensing systems have been under development for many years. For example, U.S. Pat. No. 5,210,702 discloses a system for remotely detecting carbon monoxide and carbon dioxide levels in vehicle emissions. The system used an infrared (IR) source to project a collimated beam of IR radiation through the exhaust plume of a passing vehicle. Optical apparatus was used to separate various wavelengths of the beam and direct them to particular photodetectors. Each photodetector generated an electrical signal based on the presence or absence of light of a specified wavelength. The electrical data was fed into a computer which is used to calculate and compare the ratios of carbon monoxide and carbon dioxide exhaust components. From those ratios, high emitting vehicles were identified. These ratios could also be put into a series of equations based on the stoichiometric relationships between the exhaust components which are used to compute the concentrations which would be observed by a tailpipe probe (corrected for water and any excess air).
Other methods of determining emission concentrations using remote optical gas analyzers were also attempted. One method, disclosed in U.S. Pat. No. 4,924,095, used multiple beam paths to sample a cross-sectional xe2x80x9cslicexe2x80x9d of the exhaust plume. The volume of the slice was determined and used to calculate an absolute concentration of one or more exhaust components. Such a system proved inaccurate and unworkable in practice due to irregular dispersion of the exhaust plume and significant difficulties in calculating the volume of the exhaust plume.
Remote vehicle emission testing systems have undergone many improvements since originally disclosed. Some examples include: linked video surveillance of the vehicle whose emissions were to be analyzed and license plate readers to actually xe2x80x9creadxe2x80x9d the license plate; the combination of UV and IR radiation sources for detectors with CO, CO2, NOx, water, and hydrocarbon (HC) detector channels; and various optical arrangements effecting beam splitting, beam paths, filtering, and time multiplexing.
While cars and trucks are the largest source of polluting vehicle emissions, vehicles with smaller engines, such as motorcycles, mopeds, and other small motorized vehicles may also contribute to the accumulation of pollutants in urban areas. Because the engines of small motorized vehicles typically generate considerably smaller and less dense exhaust plumes, present remote sensing systems for cars and trucks may have difficulty distinguishing exhaust readings for small motorized vehicles from background noise. For example, a 50 cc moped produces an exhaust plume ten to twenty times less than that of a small car.
Further, the spatial location of small engine exhaust plumes can be critical to successful remote sensing due to their small size and rapid dispersion. Due to the variability in the height of motorcycle exhaust outlets, a motorcycle exhaust plume may occur anywhere between 6 in. and 3 ft. above the ground. Present remote sensing systems may have difficulty targeting the exhaust plume of vehicles with small engines and variable height exhaust outlets.
These and other drawbacks of present remote emission sensing systems are overcome by one or more of the various preferred embodiments of the invention.
It is an object of the present invention to provide a system and method for detecting and measuring the relative concentrations of gases in the exhaust of moving vehicles with small engines.
This and other objects of the present invention may be achieved by a system for detecting components of the exhaust of moving vehicles. The system of the invention uses more than two beam passes through a detection space in order to generate a signal of sufficient magnitude to overcome the ambient noise in the detection space. Concentrations of one or more exhaust components may be calculated based on a ratio technique in order to render concentrations of one or more exhaust components independent of the absolute magnitude of the detector signal. The system includes a radiation source for producing a beam, optics for guiding the beam through the detection space, and a detector for receiving the beam and generating at least one signal indicative of the absorption of the beam in a wavelength band corresponding to one or more vehicle exhaust components. The system also includes a processor for obtaining information about one or more vehicle exhaust components from the generated signal or signals.
The present invention also relates to a method of detecting components in the exhaust of a moving vehicle. The method involves directing radiation through more than two passes through a detection space to a detector whereby the radiation passes through an exhaust plume located in the detection space. The next step is to generate at least one signal responsive to the radiation which passed through the exhaust plume. The at least one signal from the detector may be used to compute a ratio of the amounts of exhaust components. The ratio may be used to provide information about the emissions of a particular vehicle.
Other features and advantages of the present invention will be apparent to one of ordinary skill in the art upon reviewing the detailed description of the present invention.